The present invention relates to a power plug locking device that locks a power plug to an object, such as a vehicle, and prevents unauthorized removal of the power plug from the object.
Over these recent years, consumers have become conscious of environmental problems. Thus, vehicles that emit less carbon dioxide such as hybrid vehicles and electric vehicles have become popular. Such vehicles are driven by a battery-powered motor. When such a vehicle travels over a long distance and the state of charge of the battery becomes low, the battery must be charged (refer to Japanese Laid-Open Patent Publication No. 9-161898).
The charging of a battery involves an electrolytic reaction of compounds and ions in battery cells of the battery. This lengthens the charging time. Thus, when a user leaves the vehicle while the battery is being charged, someone may remove the power plug to steal electricity. Hence, locking devices have been developed to prevent unauthorized removal of the power plug from a vehicle.
Such a power plug locking device may include a pivotal hook-shaped lock arm and a movable lock bar. The lock arm is arranged on the power plug and prevents separation of the power plug from the inlet. The lock bar restricts movement of the lock arm. When the lock arm is hooked to a projection of the inlet, the lock bar is moved to above the lock arm to restrict movement of the lock arm. In this state, the lock bar locks the power plug to the inlet. From this state, by moving the lock bar away from the lock arm, the power plug becomes unlocked.
When the lock bar is electrically driven by a motor or the like, the lock bar may be actuated through current detection control. Referring to FIG. 8, current detection control, for example, measures the current flowing through the motor (load current value), estimates the motor rotation speed (load rotation speed) from the measured current value, and calculates the moved distance of the lock bar from the motor rotation speed. When the current continuously exceeds a threshold and the moved distance of the lock bar has reached a minimum required distance, the lock bar is determined as being located at a normal position and that overcurrent is flowing through the motor. Thus, the supply of power to the motor is stopped. The execution of such current detection control eliminates the need for sensors and allows for the power plug locking device to be reduced in size.
The calculation of the load rotation speed from the load current value uses a non-load rotation speed and non-load current value. The parameters use values taken under a condition in which the rotation of the motor is the slowest (e.g., ambient temperature of 85 degrees Celsius). This prevents erroneous determination of the lock bar being in a lock state when it is actually not in such a state.
However, under a condition in which the rotation of the motor is the fastest (e.g., ambient temperature of −40 degrees Celsius), the difference between the actual state and the calculated state becomes large. As shown in FIG. 9, repetition of locking and unlocking operations accumulates such differences. This results in the lock bar being determined through calculations as having reached its end position even though it has actually not reached such position. In such a case, the user may erroneously be notified that the lock bar has reached the end position.